1. Field of the Invention
The present invention relates to serpentine-type heat exchangers, and in particular, to louvers of fin plates of such heat exchangers.
2. Description of the Prior Art
Heat exchangers of the serpentine-type have been used for, for example, a refrigerant evaporator in an automotive air conditioning system, as shown in, for example, U.S. Pat. Nos. 4,350,025 and 4,353,224.
The serpentine-type heat exchanger comprises a flat metal tube having a refrigerant passageway or parallel passageways therein extending in a longitudinal direction of the tube. The flat tube is bent to weave up and down, or formed in a serpentine-anfractuous shape, and therefore, has a plurality of parallel portions spaced apart from one another and a plurality of U-shaped curved portions connecting adjacent ones of the parallel portions, respectively. A plurality of corrugated fin units are disposed in spaces between adjacent ones of the parallel portions of the tube and are joined thereto by brazing. Each of the corrugated fin units is formed by bending a thin plate in a corrugated form so that a number of generally parallel fin plate portions extend with gaps from one another while a number of crests are formed in opposte side surfaces of the unit alternately. The crests in the opposite sides of the unit are joined by brazing to flat side surfaces of the opposite parallel portions of the tube.
The heat exchanger is usually used together with a suitable air-flow inducing means such as a fan, blower or the like to establish a continuous flow of air from one side to the other of the heat exchanger through the gaps of each of the fin units disposed in the spaces between adjacent parallel portions of the flat tube.
Since the flat tube and each of the fin units are cooled by refrigerant flowing in the flat tube, air is cooled by heat exchange during passing through gaps in each of the fin units.
In order to improve heat exchange rate, each fin plate portion has louvers fir disturbing and deflecting air flows passing through fin units, as disclosed in, for example, U.S. Pat. No. 4,353,224.
In a known arrangement, several groups of louvers are inclined in an opposite direction to other groups of louvers so that air generally flows along a wave-like course in the fin unit. In the arrangement, since the air flow direction is deflected a number of times, air flow resistance is disadvantageously large. On the other hand, moisture in the air alow condenses on the fin plate portion, and the condensed water is carried by the wave-like air flow and is undesirably splashed outside of the heat exchanger from the air flow output end of the heat exchanger.